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Domain evolution and functional diversification of sulfite reductases
Ashita Dhillon1, Sulip Goswami, Monica Riley
1Marine Biological Laboratory, The Josephine Bay Paul Center for Comparative Molecular Biology and Evolution, Woods Hole, Massachusetts 02543, USA.
Astrobiology
|February 16, 2005
Summary
Sulfite reductases, crucial for sulfur metabolism in bacteria and archaea, diverged into four distinct enzyme clusters. This functional diversification likely predates the split between bacteria and archaea.
Area of Science:
- Biochemistry
- Microbiology
- Evolutionary Biology
Background:
- Sulfite reductases are vital enzymes in bacterial and archaeal sulfur metabolism.
- These enzymes utilize conserved domains for siroheme and iron-sulfur cluster binding, essential for electron transfer.
- Variations in siroheme-binding domain positioning distinguish different sulfite reductase types.
Purpose of the Study:
- To analyze the evolutionary divergence of sulfite reductase enzyme families.
- To understand the functional differentiation of sulfite reductases in sulfur metabolism.
- To investigate the phylogenetic relationships of sulfite reductase clusters.
Main Methods:
- Sequence analysis of the siroheme-binding domain.
- Phylogenetic analysis of sulfite reductase sequences.
- Comparative analysis of enzyme structures and functions.
Main Results:
- Sulfite reductase sequences diverged into four distinct clusters: aSir, alSir, dsr, and asrC.
- Each cluster exhibits unique biochemical properties and roles in sulfur metabolism.
- The positioning of the siroheme-binding domain differs between dissimilatory (dsrA/dsrB) and assimilatory (aSiR, asrC, alSir) enzymes.
Conclusions:
- The four sulfite reductase clusters evolved from a common ancestor with distinct biochemical functions.
- Functional diversification of sulfite reductases may have occurred before the divergence of bacteria and archaea.
- Understanding these evolutionary pathways provides insights into microbial sulfur cycling.